US20140246623A1 - Nitride phosphor and method for manufacturing the same - Google Patents

Nitride phosphor and method for manufacturing the same Download PDF

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US20140246623A1
US20140246623A1 US14/278,256 US201414278256A US2014246623A1 US 20140246623 A1 US20140246623 A1 US 20140246623A1 US 201414278256 A US201414278256 A US 201414278256A US 2014246623 A1 US2014246623 A1 US 2014246623A1
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phosphor
phosphors
satisfies
nitride phosphor
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Shiho TAKASHINA
Akihiro Ohto
Doohun Kim
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Mitsubishi Chemical Corp
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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
    • C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
    • C09K11/77—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals
    • C09K11/7766—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials containing rare earth metals containing two or more rare earth metals
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K11/00—Luminescent, e.g. electroluminescent, chemiluminescent materials
    • C09K11/08—Luminescent, e.g. electroluminescent, chemiluminescent materials containing inorganic luminescent materials
    • C09K11/0883—Arsenides; Nitrides; Phosphides

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  • This invention relates to a nitride phosphor. More specifically, the invention relates to a phosphor endowed with a luminance, internal quantum efficiency and external quantum efficiency which are all excellent.
  • the LEDs used in such applications are white-emitting LEDs composed of phosphors placed on an LED chip that emits light of a blue or near-ultraviolet wavelength. It is common to use, as this type of white-emitting LED, diodes in which yellow-emitting YAG (yttrium aluminum garnet) phosphors that utilize the blue light from a blue LED chip as the excitation light are placed on the blue LED chip.
  • YAG yttrium aluminum garnet
  • this phosphor undergoes little decrease in luminance even when the temperature rises, enabling sufficient light emission to be obtained even when excited with near-ultraviolet light. It is thus anticipated that a light-emitting device which achieves both high color rendering properties and a high efficiency can be created by using LEDs which emit light at about 350 to 420 nm in combination with phosphors that are blue, red or the like.
  • the LSN phosphor described in Patent Document 1 exhibits little decrease in luminance with a rise in temperature and moreover is able to provide sufficient luminance even when excited by near-ultraviolet light.
  • an object of this invention is to provide a nitride phosphor endowed with greater luminance, internal quantum efficiency and external quantum efficiency than conventional products.
  • the inventors have conducted durability tests in which they exposed LSN phosphors to high temperature and high humidity and checked the percent retention of luminance, discovering as a result that the luminance retention tends to get better when the phosphors are exposed to harsher conditions. Moreover, when the phosphors were treated under high-temperature and high-humidity conditions, the inventors were able to obtain the unanticipated result that the luminance and the internal quantum efficiency both rise about 10%.
  • the inventors upon analyzing phosphors in which the luminance and the internal quantum efficiency thus increased, have found that water in a hydrogen-bonded state differing from that of ordinary adsorbed water is present at the surface thereof and appears to have formed some kind of film on the phosphor surface, and have achieved this invention.
  • the present invention is as follows.
  • Ln is a rare-earth element exclusive of an element used as an activator
  • Z is an activator
  • x satisfies 2.7 ⁇ x ⁇ 3.3
  • y satisfies 5.4 ⁇ y ⁇ 6.6
  • n satisfies 10 n ⁇ 12
  • the nitride phosphor having an infrared absorption spectrum as measured by a diffuse reflectance method at measurement intervals of 2 cm ⁇ 1 or less, that satisfies the following condition:
  • Ln is a rare-earth element exclusive of an element used as an activator
  • Z is an activator
  • x satisfies 2.7 ⁇ x ⁇ 3.3
  • y satisfies 5.4 ⁇ y ⁇ 6.6
  • n satisfies 10 ⁇ n ⁇ 12
  • thermogravimetry at least 25% of total adsorbed water that has adsorbed to the nitride phosphor desorbs at between 170° C. and 300° C.
  • nitride phosphor according to ⁇ 2> wherein at least 30% of the total adsorbed water desorbs at between 170° C. and 300° C.
  • Ln is a rare-earth element exclusive of an element used as an activator
  • Z is an activator
  • x satisfies 2.7 ⁇ x ⁇ 3.3
  • y satisfies 5.4 ⁇ y ⁇ 6.6
  • n satisfies 10 ⁇ n ⁇ 12
  • the ratio of a specific surface area determined by a BET method with respect to a specific surface area calculated from an average particle diameter measured by a Coulter counter method is 20 or less.
  • nitride phosphor according to any one of ⁇ 1> to ⁇ 4>, wherein the nitride phosphor has an internal quantum efficiency of at least 71%.
  • Ln is a rare-earth element exclusive of an element used as an activator
  • Z is an activator
  • x satisfies 2.7 ⁇ x ⁇ 3.3
  • y satisfies 5.4 ⁇ y ⁇ 6.6
  • n satisfies 10 ⁇ n ⁇ 12
  • a method of manufacturing a nitride phosphor comprising the steps of:
  • nitride phosphor a nitride phosphor of general formula (1) below
  • Ln is a rare-earth element exclusive of an element used as an activator
  • Z is an activator
  • x satisfies 2.7 ⁇ x ⁇ 3.3
  • y satisfies 5.4 ⁇ y ⁇ 6.6
  • n satisfies 10 ⁇ n ⁇ 12
  • a phosphor including ⁇ -SiAlON, ⁇ -SiAlON, CaAlSiN 3 or CaAlSi 4 N 7 as a host.
  • a nitride phosphor having an infrared absorption spectrum, as measured by a diffuse reflectance method at measurement intervals of 2 cm ⁇ 1 or less, that satisfies the following condition:
  • a nitride phosphor wherein, in thermogravimetry, at least 25% of total adsorbed water that has adsorbed to the nitride phosphor desorbs at between 170° C. and 300° C.
  • a nitride phosphor wherein the ratio of a specific surface area determined by a BET method with respect to a specific surface area calculated from an average particle diameter measured by a Coulter counter method is 20 or less.
  • nitride phosphor according to any one of ⁇ 9> to ⁇ 11>, wherein the nitride phosphor has an internal quantum efficiency of at least 71%.
  • nitride phosphor according to ⁇ 1> wherein the ratio of a specific surface area determined by a BET method with respect to a specific surface area calculated from an average particle diameter measured by a Coulter counter method is 20 or less.
  • nitride phosphor according to ⁇ 2> or ⁇ 3> wherein the ratio of a specific surface area determined by a BET method with respect to a specific surface area calculated from an average particle diameter measured by a Coulter counter method is 20 or less.
  • nitride phosphor according to ⁇ 9> or ⁇ 10> wherein the ratio of a specific surface area determined by a BET method with respect to a specific surface area calculated from an average particle diameter measured by a Coulter counter method is 20 or less.
  • nitride phosphors of improved luminance, internal quantum efficiency and external quantum efficiency there can also be provided a method of manufacturing nitride phosphors of improved luminance and internal quantum efficiency.
  • FIG. 1 is a graph which compares the values obtained by converting the infrared absorption spectra of the phosphors in Example 1 of the invention and Comparative Example 1 into Kubelka-Munk function values.
  • FIG. 2 is a graph which compares the values obtained by converting the infrared absorption spectra of the phosphors in Example 2 of the invention and Comparative Example 2 into Kubelka-Munk function values.
  • FIG. 3 is a graph which compares the values obtained by converting the infrared absorption spectra of the phosphors in Example 3 of the invention and Comparative Example 3 into Kubelka-Munk function values.
  • FIG. 4 is a graph which compares the values obtained by converting the infrared absorption spectra of the phosphors in Example 4 of the invention and Comparative Example 4 into Kubelka-Munk function values.
  • FIG. 5 is a graph which compares the values obtained by converting the infrared absorption spectra of the phosphors in Example 5 of the invention and Comparative Example 5 into Kubelka-Munk function values.
  • FIG. 6 is a graph which shows the values obtained by converting the infrared absorption spectrum of the phosphor in Example 6 of the invention into Kubelka-Munk function values.
  • FIG. 7 is a graph which plots the values obtained by converting the infrared absorption spectra of the phosphors in Examples 1 to 6 of the invention and Comparative Examples 1 to 5 into Kubelka-Munk function values, and dividing the differential average values thereof in the range of 3593 cm ⁇ 1 to 3608 cm ⁇ 1 by the maximum values thereof in the range of 3500 cm ⁇ 1 to 3250 cm ⁇ 1 .
  • FIG. 8 is a graph showing the results obtained by measuring the quantity of adsorbed water on the phosphors in Example 1 of the invention and Comparative Example 1 that desorbs in various temperature ranges.
  • FIG. 9 is a graph that compares the values obtained by converting the infrared absorption spectra of the phosphors in Example 9 of the invention and Comparative Example 9 into Kubelka-Munk function values.
  • FIG. 10 is a graph that compares the values obtained by converting the infrared absorption spectra of the phosphors in Example 10 of the invention and Comparative Example 10 into Kubelka-Munk function values.
  • FIG. 11 is a graph that compares the values obtained by converting the infrared absorption spectra of the phosphors in Example 11 of the invention and Comparative Example 11 into Kubelka-Munk function values.
  • FIG. 12 is a graph that compares the values obtained by converting the infrared absorption spectra of the phosphors in Example 12 of the invention and Comparative Example 12 into Kubelka-Munk function values.
  • FIG. 13 is a graph that compares the values obtained by converting the infrared absorption spectra of the phosphors in Example 13 of the invention and Comparative Example 13 into Kubelka-Munk function values.
  • FIG. 14 is a graph which plots the values obtained by converting the infrared absorption spectra of the phosphors in Examples 1 to 6 and 9 to 13 of the invention and Comparative Examples 1 to 5 and 9 to 13 into Kubelka-Munk function values, and dividing the differential average values thereof in the range of 3593 cm ⁇ 1 to 3608 cm ⁇ 1 by the maximum values thereof in the range of 3500 cm ⁇ 1 to 3250 cm ⁇ 1 .
  • FIG. 15 is a graph showing the results obtained by measuring the quantity of adsorbed water on the phosphors in Example 9 of the invention and Comparative Example 9 that desorbs in various temperature ranges.
  • FIG. 16 is a graph showing the results obtained by measuring the quantity of adsorbed water on the phosphors in Example 10 of the invention and Comparative Example 10 that desorbs in various temperature ranges.
  • FIG. 17 is a graph showing the results obtained by measuring the quantity of adsorbed water on the phosphors in Example 11 of the invention and Comparative Example 11 that desorbs in various temperature ranges.
  • FIG. 18 is a graph showing the results obtained by measuring the quantity of adsorbed water on the phosphors in Example 12 of the invention and Comparative Example 12 that desorbs in various temperature ranges.
  • FIG. 19 is a graph showing the results obtained by measuring the quantity of adsorbed water on the phosphors in Example 13 of the invention and Comparative Example 13 that desorbs in various temperature ranges.
  • the inventive phosphor is characterized by the presence, on the surface of a nitride phosphor, and preferably on the surface of a phosphor of the subsequently described general formula (1), of a special adsorbed water that is predicted to have, unlike ordinary water, multiple types of hydrogen bonds. Because this adsorbed water does not evaporate in the normal temperature range, and instead begins to desorb from the phosphor surface when the phosphor is exposed to elevated temperatures of at least 170° C. that greatly exceed the normal temperature for water evaporation of 100° C., this adsorbed water does not vanish under ordinary conditions of phosphor use.
  • the luminance and interior quantum efficiency of the phosphor increase.
  • the inventors surmise the reason for such increases in the luminance and interior quantum efficiency of the phosphor to be that, with the presence of adsorbed water, a thin layer of water having a lower refractive index than the phosphor forms on the phosphor surface, leading to an increase in the light extraction ratio from the phosphor interior.
  • This thin layer of water itself characterizes the phosphor of the invention. It is a first aspect of the invention to have differentiated between this thin layer of special water and a layer of ordinary water using infrared absorption spectra.
  • the thin layer of water formed on the phosphor surface can be distinguished from the spectrum obtained by carrying out infrared absorption spectroscopy by the diffuse reflectance method. Specifically, the presence or absence of a thin layer of water on the phosphor can be determined by the characteristics of having a broad peak in the range of 3250 cm ⁇ 1 to 3500 cm ⁇ 1 indicative of the formation of hydrogen bonds, and of exhibiting the rise of a sharp peak particularly near 3600 cm ⁇ 1 .
  • infrared absorption spectroscopy by the diffuse reflectance method is carried out. It is critical for the measurement intervals at this time to be set to 2 cm ⁇ 1 or less. At measurement intervals wider than 2 cm ⁇ 1 , the precision will be inadequate for confirming the presence of the thin layer of special water of the invention. Hence, it is critical that such spectroscopy be carried out at measurement intervals of 2 cm ⁇ 1 or less.
  • the spectrum obtained by the diffuse reflectance measurement of a powder provides data that accentuates the peak intensities of weak absorption bands. Therefore, when carrying out quantitative comparisons, it is common to convert the diffusion reflectance spectrum results with the Kubelka-Munk function to values (Kubelka-Munk function values) that can be compared with a transmission spectrum (see, for example, paragraph [0101] of Japanese Patent Application Laid-open No. 2010-214289).
  • ordinary water appears as a peak at about 3300 cm ⁇ 1 .
  • a broad peak appears over a range of 3250 cm ⁇ 1 to 3500 cm ⁇ 1 as a peak in which the vicinity of the peak apex has a flat shape as if the top of an ordinary peak had been squashed.
  • a peak having a flat top indicates that waters having multiple types of hydrogen bonds in this peak range are all present in about equal amounts, which may be regarded as a state considerably different from the state in which ordinary water is present.
  • the infrared absorption spectrum of the phosphor is measured by the diffuse reflectance method.
  • the measurement conditions include setting the measurement intervals to 2 cm ⁇ 1 or less. For measurement at a sufficient precision, it is necessary to set the measurement intervals to, at a minimum, 2 cm ⁇ 1 or less.
  • the apparatus used to measure the infrared absorption spectrum of the phosphor is not subject to any particular limitation, provided it is one based on the principles of the diffusion reflectance method.
  • an AVATOR 360 spectrometer (Nicolet) may be used.
  • Conversion to Kubelka-Munk function values can be carried out using conversion software that is generally installed in the spectrometer.
  • Step (a) calculates, for Kubelka-Munk function values converted from an infrared absorption spectrum obtained by the diffuse reflectance method, the slopes (referred to below as “differential values”) between two adjoining measured values in the range of 3593 cm ⁇ 1 to 3608 cm ⁇ 1 .
  • the range of 3593 cm ⁇ 1 to 3608 cm ⁇ 1 is a portion of the spectrum corresponding to the rise, or edge, of the peak just before the peak for the multiple types of hydrogen bonds, and this slope (differential value) refers to the slope of the rise in the peak for multiple types of hydrogen bonds.
  • the reason for determining the average of differential values between two adjoining measured values in a given range, i.e., 3593 cm ⁇ 1 to 3608 cm ⁇ 1 is to avoid not having the characteristics of this invention be accurately expressed. That is, in cases where a specific numerical value, such as the slope at 3600 cm ⁇ 1 , is used or where the slope between 3593 cm ⁇ 1 and 3608 cm ⁇ 1 is calculated, owing to the influence of the degree of instability in measurement, the shape of the actual peak may fail to be represented.
  • Step (b) determines the maximum value in the range of 3500 cm ⁇ 1 to 3250 cm ⁇ 1 for the Kubelka-Munk function values obtained by such measurement.
  • the range of 3500 cm ⁇ 1 to 3250 cm ⁇ 1 indicates the range of the flat peak.
  • Step (b) computes the maximum value in the range of this peak.
  • Step (c) computes a value by dividing the average of the differential values obtained in Step (a) by the maximum value obtained in Step (b).
  • the peak intensity of the infrared absorption spectrum differs according to the measurement conditions; if the peak intensity is low, the average of the differential values becomes small.
  • suitable evaluation was enabled even when, in measurement of the infrared absorption spectrum, the overall measurement intensity level was low or was too high.
  • the step for doing this is (c), and the numerical value of the criterion for deciding whether a phosphor is the phosphor of the invention, that is, the value obtained by dividing the average differential value by the maximum peak intensity, is ⁇ 2.4 ⁇ 10 ⁇ 3 or less.
  • this thin layer of special water and a layer of ordinary water are differentiated by the temperature at which the adsorbed water desorbs.
  • the inventive phosphor is a nitride phosphor, and is preferably a nitride phosphor of subsequently described general formula (1) wherein, in thermogravimetry, at least 25% of the total adsorbed water that has adsorbed to the phosphor desorbs at between 170° C. and 300° C. Preferably at least 30%, and more preferably at least 35%, of the total adsorbed water that has adsorbed to the phosphor desorbs at between 170° C. and 300° C.
  • the adsorbed water present on the surface of the inventive phosphor does not evaporate much at the normal water evaporation temperature of 100° C., but readily desorbs from the phosphor surface when exposed to elevated temperatures of at least 170° C.
  • the copious adsorbed water that desorbs at between 170° C. and 300° C. in thermogravimetry is a characteristic of this invention, and the fact that at least 25%, and preferably at least 30%, of the total adsorbed water that has adsorbed to the phosphor desorbs at between 170° C. and 300° C. characterizes the invention.
  • thermogravimetry of the emitted gases analyzed in thermal programmed desorption (TPD), that portion having a molecular weight of 18 is regarded as adsorbed water. Measurement is carried out over the range of room temperature to 1000° C., and the quantity of gas having a molecular weight of 18 that has been emitted in the range up to 1000° C. is regarded as the total quantity of adsorbed water. The temperature rise rate is set to 33° C./min. By dividing the quantity of gas having a molecular weight of 18 emitted at between 170° C. and 300° C. by the quantity of gas having a molecular weight of 18 emitted at between room temperature and 1000° C., it is possible to determine the ratio of the invention. Because the units of the measured values are the same, this ratio (%) is dimensionless.
  • thermogravimetry measurement is often carried out using an apparatus such as a TG-DTA.
  • TG it is difficult to know what substance desorbs from the phosphor, in addition to which there is a weight gain due to oxidation at the surface of the nitride phosphor. For these reasons, it is necessary in this invention to use TPD and measure the quantity of gas having a molecular weight of 18.
  • the quantity of water that desorbs from 170° C. to 300° C. is unlikely to exceed 25%, and certainly does not exceed 30%. Accordingly, it is possible to check for the presence of multiple types of hydrogen bonds on the phosphor surface that characterizes this invention.
  • Thermogravimetry may be carried out by, for example, analyzing the adsorbed gases using a gas analyzer for phosphor analysis (ANELVA) or the like.
  • a phosphor according to the third aspect of the invention is differentiated by the fact that the difference between the specific surface area determined by the BET method and the specific surface area computed from the average particle diameter measured by the Coulter counter method becomes a very small value that cannot be obtained by other methods.
  • the inventive phosphor is a nitride phosphor, and is preferably a nitride phosphor of the subsequently described general formula (1) wherein the ratio of the specific surface area determined by the BET method with respect to the specific surface area calculated from the average particle diameter measured by the Coulter counter method is 20 or less.
  • Phosphors such as the phosphors of the subsequently described general formula (1), generally have a large difference between both above specific surface area values.
  • the ratio between these two specific surface areas is a small value of 20 or less. This is presumably because the special adsorbed water of this invention covers most of the phosphor surface, resulting in the burial of nitrogen adsorption sites and, in turn, a decrease in the amount of nitrogen adsorption at the time of BET measurement, ultimately yielding such a small ratio.
  • the average particle diameter determined by the Coulter counter method is the volume median diameter, and the surface area determined from this average particle diameter is given by the following formula.
  • the specific surface area calculated with this formula is determined based on the assumption that the surface of the phosphor is a smooth spherical surface free of irregularities, whereas the specific surface area determined by the BET method is a value reflecting actual irregularities that has been determined from the amount of nitrogen adsorption onto the particle surface.
  • Measurement of the average particle diameter by the Coulter counter method may be carried out using, for example, a Coulter counter particle size analyzer.
  • the phosphors of the invention prefferably have an internal quantum efficiency of at least 71%.
  • the internal quantum efficiency is explained in, for example, paragraphs [0068] to [0083] of Patent Document 1.
  • the internal quantum efficiency is generally determined by the following formula.
  • the internal quantum efficiency is a value that incorporates the ease of extracting light from the phosphor.
  • the light extraction efficiency increases, as a result of which the value of the internal quantum efficiency also appears to improve.
  • the internal quantum efficiency of the inventive phosphor it is preferable for the internal quantum efficiency of the inventive phosphor to be a high value, and especially 71% or more.
  • the number of photons used in measurement of the internal quantum efficiency can be measured using a spectrometer such as the MCPD 2000 or the MCPD 7000 manufactured by Otsuka Electronics Co., Ltd.
  • the phosphors used in this invention are nitride phosphors, and most preferably are phosphors having a basic structure of general formula (1) below.
  • Ln is a rare-earth element exclusive of the element used as the activator
  • Z is an activator
  • x satisfies 2.7 ⁇ x ⁇ 3.3
  • y satisfies 5.4 ⁇ y ⁇ 6.6
  • n satisfies 10 ⁇ n ⁇ 12.
  • the aforementioned Ln is preferably a rare-earth element containing 80 mol % or more of La, more preferably a rare-earth element containing 95 mol % or more of La, and even more preferably La.
  • elements other than the La included in Ln may be used without difficulty, provided they are rare-earth elements.
  • Preferred elements include yttrium, gadolinium and the like which are commonly substituted in other phosphors as well. These elements are desirable because they have ionic radii close to that of La and the charge is uniform.
  • the activator Z preferably includes europium (Eu) and cerium (Ce), more preferably includes at least 80 mol % of Ce, even more preferably includes at least 95 mol %, and is most preferably Ce.
  • the molar ratio of the elements i.e., the ratio of x, y and n denoting the stoichiometric composition, is 3:6:11. Because use as a phosphor is possible even with an excess or insufficiency therein of about 10%, the values for x, y and n are set in the respective ranges of 2.7 ⁇ x ⁇ 3.3, 5.4 ⁇ y ⁇ 6.6, and 10 ⁇ z ⁇ 12.
  • the inventive phosphors are nitride phosphors, and preferably ones having the above-described general formula (1), although phosphors in which a portion of the sites have been substituted with alkaline earth metal elements such as calcium or strontium, or with aluminum or the like for such purposes as to change the chromaticity point are not excluded from the range of the invention.
  • alkaline earth metal elements such as calcium or strontium, or with aluminum or the like for such purposes as to change the chromaticity point
  • substitution with calcium, yttrium, gadolinium or strontium which may be used when lengthening the emission wavelength.
  • These elements are sometimes substituted at the same time with other elements in order to satisfy the principle of conservation of charge.
  • some of the Si and N sites are sometimes substituted with oxygen or the like.
  • Phosphors such as these may also be advantageously used.
  • nitride phosphors have a high refractive index compared with other phosphors
  • similar effects are not limited to phosphors of general formula (1) and can probably be obtained in other nitride phosphors as well.
  • nitride phosphors include phosphors containing ⁇ -SiAlON, ⁇ -SiAlON, CaAlSiN 3 , CaAlSi 4 N 7 or Sr 2 Si 5 N 8 as the host.
  • the effects of the invention can probably be obtained even when a portion of these elements is substituted with another element such as oxygen, or a portion is substituted with another element for charge compensation.
  • the special water film of the invention is provided on the surface of these phosphors, it is preferable to carry out coating or surface treatment such as to increase the number of hydroxyl groups on the surface.
  • the phosphors of the invention have a volume median diameter that is generally at least 0.1 ⁇ m, and preferably at least 0.5 ⁇ m, and is generally not more than 35 ⁇ m, and preferably not more than 25 ⁇ m. If the volume median diameter is too small, the luminance decreases and the phosphor particles have a tendency to agglomerate. On the other hand, if the volume median diameter is too large, non-uniform coating and the clogging of equipment such as dispensers has a tendency to arise. Hence, a volume median diameter within the above range is preferred.
  • the volume median diameter can be measured by, for example, the above-described Coulter counter method.
  • a typical apparatus that may be used to carry out measurement includes, for example, the Multisizer (Beckman Coulter).
  • the inventive phosphor is subjected to heat treatment so as to form a thin water layer having multiple types of hydrogen bonds on the phosphor surface.
  • production may be carried out by a known production method, such as that described in Patent Document 1 or that described in Patent Document 2.
  • it can be produced by mixing phosphor precursors as appropriate, which were prepared as the raw materials, and firing the mixed phosphor precursors (firing step).
  • production is carried out by preferably a method in which an alloy is used as at least some portion of the raw materials, and more preferably a method having a step in which an alloy containing at least an Ln element, a Z element and the Si element in above formula (1) (sometimes referred to below as a “phosphor-producing alloy”) is fired in the presence of a flux.
  • the phosphors of the invention can be produced using some or all of such a raw material as a phosphor-producing alloy.
  • Patent Document 2 describes in detail methods for producing such starting alloys, and provides detailed descriptions of methods capable of utilizing, where necessary, such operations as the production, size reduction and classification of starting alloys.
  • the firing step is preferably carried out in a hydrogen-containing nitrogen gas atmosphere. Moreover, after firing, it is preferable to wash the fired product with an acidic aqueous solution.
  • compositions of metal elements contained in an alloy for producing a phosphor coincides with the composition of the metal elements contained in the crystal phase represented by the above formula (1), only the alloy for producing a phosphor may be fired.
  • an alloy for producing a phosphor is not used or the compositions are different, an alloy for producing a phosphor having a different composition, elemental metal, or metal compound can be mixed with the alloy for producing a phosphor so that the composition of the metal elements contained in the material coincides with the composition of the metal elements contained in the crystal phase represented by the formula (1). Firing is then performed.
  • metal compounds that are used for other than an alloy for producing a phosphor
  • the metal compound may be exemplified by nitrides, oxides, hydroxides, carbonates, nitrates, sulfates, oxalates, carboxylates, halides, etc.
  • a suitable one can be selected, in light of reactivity with the target compound or the level of NO x , SO x , or the like generated at the time of firing.
  • a nitride and/or an oxynitride as the phosphor of the present invention is a nitrogen-containing phosphor.
  • a nitride is preferably used in order to function as a nitrogen source as well.
  • nitride and oxynitride examples include: nitrides of elements constituting the phosphor such as LaN, Si 3 N 4 and CeN; and complex nitrides of elements constituting the phosphor such as La 3 Si 4 N 11 and LaSi 3 N 5 .
  • the abovementioned nitrides may contain a small amount of oxygen.
  • the ratio (molar ratio) of oxygen/(oxygen+nitrogen) in the nitride, insofar as the phosphor of the present invention can be produced.
  • the ratio is usually 5% or smaller, preferably 1% or smaller, more preferably 0.5% or smaller, still more preferably 0.3% or smaller, particularly preferably 0.2% or smaller. In a case where the ratio of oxygen is too large, the degree of brightness may decrease.
  • the host of the inventive phosphor can be obtained.
  • firing here is preferably carried out in a hydrogen-containing nitrogen gas atmosphere.
  • flux is preferably added to the reaction system in order to secure growth of good quality crystals.
  • the type of flux is not particularly limited and includes, for example, ammonium halides such as NH 4 Cl and NH 4 F.HF; alkali metal carbonates such as NaCO 3 and LiCO 3 ; alkali metal halides such as LiCl, NaCl, KCl, CsCl, LiF, NaF, KF and CsF; alkaline earth metal halides such as CaCl 2 , BaCl 2 , SrCl 2 , CaF 2 , BaF 2 , SrF 2 , MgCl 2 and MgF 2 ; alkaline earth metal oxides such as BaO; boron oxide, boric acid and borate compounds of alkali metals or alkaline earth metals such as B 2 O 3 , H 3 BO 3 and Na 2 B 4 O 7 ; phosphate compounds such as Li 3 PO 4 and NH 4 H 2 PO 4 ; aluminum halides such as AlF 3 ; zinc compounds such as zinc halides (e.g., ZnCl
  • the flux include: halides of rare-earth elements such as LaF 3 , LaCl 3 , GdF 3 , GdCl 3 , LuF 3 , LuCl 3 , YF 3 , YCl 3 , ScF 3 , and ScCl 3 ; and oxides of rare-earth elements such as La 2 O 3 , Gd 2 O 3 , Lu 2 O 3 , Y 2 O 3 , and Sc 2 O 3 .
  • halides of rare-earth elements such as LaF 3 , LaCl 3 , GdF 3 , GdCl 3 , LuF 3 , LuCl 3 , YF 3 , YCl 3 , ScF 3 , and ScCl 3
  • oxides of rare-earth elements such as La 2 O 3 , Gd 2 O 3 , Lu 2 O 3 , Y 2 O 3 , and Sc 2 O 3 .
  • the above flux is preferably halides, and specific examples are preferably alkali metal halides, alkaline-earth metal halides, Zn halides, and rare-earth element halides. Of the halides, fluoride and chloride are preferred.
  • these fluxes can be used either as a single one or as a mixture of two or more kinds in any combination and in any ratio.
  • More preferred fluxes include MgF 2 .
  • preferred use can also be made of, for example, CeF 3 , LaF 3 , YF 3 and GdF 3 .
  • CeF 3 , LaF 3 , YF 3 and GdF 3 are preferred use.
  • YF 3 , GdF 3 and the like have the effect of changing the chromaticity coordinates (x, y) of the emission color.
  • cesium carbonate and/or cesium nitrate is also preferred.
  • magnesium fluoride has an outstanding action as a flux, it is not without its side effects.
  • the magnesium ions included in magnesium fluoride are ions having a smaller ionic radius than the lanthanum ions making up the host, and thus have a tendency to substitute for La in the LSN or to infiltrate the crystal lattice and remain behind as impurities, which lowers the strain and crystallinity of the crystal lattice and becomes a cause of nonluminescent radiation, lowering the luminance of the phosphor.
  • the rubidium ions have a very large ionic radius (compared with the Shannon ionic radius of hexacoordinate La 3+ of 117 pm, Rb + has an ionic radius of 166 pm), making it possible to substantially eliminate this side effect of lower luminance due to the entry of such ions into the crystal.
  • This is clearly demonstrated by the fact that, even with elemental analysis in which the LSN phosphors are dissolved after thorough washing of the phosphors, substantially no rubidium is detected from LSN phosphors obtained by firing with the use of a Rb-containing flux.
  • One conceivable factor is that because rubidium compounds have relatively low melting points, their action as a flux can be obtained from a low temperature.
  • the raw material mixture is generally charged into a vessel such as a crucible or a tray, and is placed in a heating furnace capable of atmospheric control.
  • the container material is preferably one having a low reactivity with metal compounds, such as boron nitride, silicon nitride, carbon, aluminum nitride, molybdenum or tungsten. Of these, molybdenum and boron nitride are preferred because of their excellent corrosion resistance.
  • the above material may be of a single type used alone, or two or more types may be used in any combination and proportions.
  • the shape of the firing vessel to be used is optional.
  • its bottom may be circular or oval with no angles, or may be of polygonal shape such as triangular or quadrangular.
  • the height of the firing vessel either, insofar as it can be accommodated in a heating furnace. It can be high or low. Among these, the shape having good heat dissipation properties is preferred.
  • a fired nitride phosphor By firing the raw material mixture, a fired nitride phosphor can be obtained.
  • the above raw material mixture is preferably fired while held at a volume packing ratio of 40% or less.
  • the volume packing fraction (%) can be determined as (bulk density of mixture powder)/(theoretical density of mixed powder) ⁇ 100.
  • the firing vessel filled with a raw material mixture of this phosphor is held in a firing instrument (hereinafter may be referred to as “furnace”).
  • a firing instrument hereinafter may be referred to as “furnace”.
  • the firing instrument There is no special limitation on the firing instrument, insofar as the advantageous effect of the present invention is not impaired.
  • an instrument which permits easy control of an atmosphere in the instrument and easy control of pressure For example, a hot isostatic pressing device (HIP), a resistance heating vacuum pressurized atmosphere heat treatment furnace or the like is preferred.
  • HIP hot isostatic pressing device
  • a resistance heating vacuum pressurized atmosphere heat treatment furnace or the like is preferred.
  • a gas containing nitrogen is allowed to pass through the firing instrument before initiation of heating to replace a gas in the system sufficiently with the nitrogen-containing gas.
  • the nitrogen-containing gas may be allowed to pass if necessary after the system is evacuated.
  • the nitrogen-containing gas used during nitriding treatment is a gas containing the element nitrogen, such as nitrogen, ammonia or a mixed gas of nitrogen and hydrogen.
  • the nitrogen-containing gas may be of a single type used alone, or may be of two or more types used in any combination and proportions. Of these a nitrogen gas that contains hydrogen (a hydrogen-containing nitrogen gas) is preferred as the nitrogen-containing gas.
  • a mixing ratio of hydrogen in the hydrogen-containing nitrogen gas of 4 vol % or less falls outside the explosion range and is preferred from the standpoint of safety.
  • Nitriding treatment is carried out by heating the phosphor raw materials in a system that is charged with a hydrogen-containing nitrogen gas or through which a hydrogen-containing nitrogen gas is passed.
  • the pressure at this time may be a somewhat depressurized state relative to atmospheric pressure, atmospheric pressure or a pressurized state.
  • the hydrogen-containing nitrogen gas it is preferable for the hydrogen-containing nitrogen gas to have a gauge pressure of at least 0.1 MPa. Alternatively, heating may be carried out under an elevated pressure of at least 20 MPa. A pressure of 200 MPa or less is preferred.
  • Nitrogen-containing gas is then passed through the system so as to thoroughly flush the interior of the system. If necessary, gas may be passed through after first evacuated the interior of the system. Conditions for this nitriding treatment, such as the rate of temperature rise during the nitriding reaction, the initial nitriding method, the firing temperature and the holding time, are carefully described in, for example, the above-mentioned Patent Document 1 and Patent Document 2, and so production may be carried out based on these descriptions.
  • Steps other than described above can be carried out in the production method according to the present invention if necessary.
  • a pulverization step, washing step, classification step, surface treatment step, drying step or the like can be carried out if necessary after the above-mentioned firing step.
  • Pulverizing can be done using, for example, a pulverizers such as a hammer mill, a roll mill, a ball mill, a jet mill, a ribbon blender, a V-type blender, a Henschel mixer, or using a mortar and a pestle.
  • a pulverizers such as a hammer mill, a roll mill, a ball mill, a jet mill, a ribbon blender, a V-type blender, a Henschel mixer, or using a mortar and a pestle.
  • a pulverizers such as a hammer mill, a roll mill, a ball mill, a jet mill, a ribbon blender, a V-type blender, a Henschel mixer, or using a mortar and a pestle.
  • a ball milling using, for example, a container made of alumina, silicon nitride, ZrO 2 , glass or the like and balls made of the same material as the container, iron-core
  • Washing of a phosphor surface can be done using, for example, water such as deionized water, organic solvent such as ethanol, or alkaline aqueous solution such as ammonia water.
  • Acidic aqueous solutions containing inorganic acids such as hydrochloric acid, nitric acid, sulfuric acid, aqua regia, or a mixture of hydrofluoric acid and sulfuric acid; and organic acids such as acetic acid may be used, for example, for the purpose of removing an impurity phase, such as the flux used, attached to the phosphor surface and improving the luminescent characteristics.
  • An acidic aqueous solution containing hydrofluoric acid, ammonium fluoride (NH 4 F), ammonium hydrogen fluoride (NH 4 HF 2 ), sodium hydrogen fluoride, potassium hydrogen fluoride and the like may be used for the purpose of removing the noncrystalline content that is an impurities phase.
  • an aqueous solution of NH 4 HF 2 is preferred.
  • the concentration of the aqueous solution of NH 4 HF 2 is generally from 1 wt % to 30 wt %, and preferably from 5 wt % to 25 wt %. If necessary, these chemicals may be suitably mixed and used. Where necessary, temperature control of these acidic aqueous solutions is preferred.
  • the luminance, emission intensity, absorption efficiency, and object color of the phosphor can be improved by the above-described washing step.
  • the fired product after being washed, is agitated for 1 hour in a 10-fold amount of a 10 wt % NH 4 HF 2 aqueous solution, then dispersed in water and left to stand for 1 hour, after which it is preferable to wash the resulting supernatant until the pH thereof becomes approximately neutral (about pH 5 to 9).
  • the supernatant is either basic or acidic, there is a possibility that, when mixed with the subsequently described liquid medium or the like, it will exert an adverse effect on the liquid medium.
  • a method of washing with a first type of liquid then washing with a second type of liquid, or a method of washing with a liquid obtained by mixing together two or more types of substances is preferred for removing impurities that arise during acid washing.
  • the former is exemplified by the steps of washing with an aqueous solution of NH 4 HF 2 , then washing in hydrochloric acid, and finally rinsing with water.
  • the latter is exemplified by the steps of washing with a mixed aqueous solution of NH 4 HF 2 and HNO 3 , then rinsing with water.
  • the degree of the washing may be represented in the electric conductivity of the supernatant that can be obtained after one hour settling period after dispersion in water 10 times by weight of the phosphor after the washing.
  • the electric conductivity is measured as follows.
  • the phosphor particles which have larger specific gravity than water, are allowed to precipitate spontaneously, by leaving them to stand for 1 hour after they are stirred for dispersion in water which is 10 times as heavy as the phosphor for a predetermined period of time, for example, 10 minutes.
  • the electric conductivity of the supernatant fluid at that time may be, for example, measured using a conductance meter, “EC METER CM-30G”, manufactured by DKK-TOA CORPORATION or the like.
  • demineralized water or distilled water is preferred. Among them, water with low electric conductivity is particularly preferred.
  • water of which the electric conductivity is usually 0.0064 mS/m or higher, usually 1 mS/m or lower, and preferably 0.5 mS/m or lower.
  • the electric conductivity is usually measured at a room temperature (around 25° C.)
  • Classification treatment can be done by, for example, levigation, or using various classifiers such as air current classifier or vibrating sieve. Particularly, a dry classification using a nylon mesh can be preferably used to obtain the phosphor of good dispersibility with volume mean diameter of about 10 ⁇ m.
  • combination of a dry classification using nylon mesh and elutriation treatment can obtain the phosphor of good dispersibility with volume-average median diameter of about 20 ⁇ m.
  • phosphor particles is dispersed in an aqueous medium at a concentration of around 0.1 weight % to 10 weight %.
  • the pH of the aqueous medium is set at usually 4 or larger, preferably 5 or larger, and usually 9 or smaller, preferably 8 or smaller in order to prevent the degradation of the phosphor.
  • the lower limit of the particle size for performing the sieving process is usually 1 ⁇ m or larger, and preferably 5 ⁇ m or larger.
  • the phosphors are dried at about 100° C. to 200° C. If necessary, dispersion treatment (e.g., passing through a mesh) may be carried to a degree that prevents agglomeration on drying.
  • dispersion treatment e.g., passing through a mesh
  • the phosphors of the invention are characterized by the presence of special adsorbed water on the phosphor surface.
  • Phosphors having such special adsorbed water present thereon can be obtained by vapor heat treatment in which the phosphors produced in the foregoing steps are left to stand in the presence of a vapor, and preferably in the presence of water vapor.
  • the temperature is generally at least 50° C., preferably at least 80° C., and more preferably at least 100° C., and is generally 400° C. or less, preferably 300° C. or less, and more preferably 200° C. or less. If the temperature is too low, the desirable effects owing to the presence of adsorbed water at the phosphor surfaces tend to be difficult to obtain, whereas if the temperature is too high, the surfaces of the phosphor particles sometimes become rough.
  • the humidity is generally at least 50%, preferably at least 80%, and most preferably 100%. If the humidity is too low, the desirable effects owing to the presence of adsorbed water at the phosphor surfaces tend to be difficult to obtain. So long as the desirable effects of adsorbed water layer formation can be obtained, an aqueous phase may also be present together with the vapor phase having a humidity of 100%.
  • the pressure is generally at least atmospheric pressure, preferably at least 0.12 MPa, and more preferably at least 0.3 MPa, and is generally 10 MPa or less, preferably 1 MPa or less, and more preferably 0.5 MPa or less. If the pressure is too low, the desirable effects owing to the presence of adsorbed water at the phosphor surfaces tend to be difficult to obtain, whereas if the pressure is too high, a large-scale treatment apparatus is required and problems sometimes arise with the safety of the operation.
  • the holding time is generally at least 0.5 hours, preferably at least 1 hour, and more preferably at least 1.5 hours, and is generally 200 hours or less, preferably 100 hours or less, more preferably 12 hours or less, and still more preferably 5 hours or less.
  • the method of carrying out the vapor heating step while satisfying the above conditions is exemplified by the method of placing the phosphors in an autoclave under a high humidity and a high pressure.
  • an apparatus such as a pressure cooker that can set the phosphors under high-temperature and humidity conditions to the same degree as an autoclave.
  • the pressure cooker used may be, for example, a TPC-412M (ESPEC Corp.), with which it is possible to control the temperature to from 105° C. to 162.2° C., the humidity to from 75 to 1000 (depending on the temperature conditions), and the pressure to from 0.020 MPa to 0.392 MPa (0.2 kg/cm 2 to 4.0 kg/cm 2 ).
  • the pressure is at least normal pressure (0.1 MPa) and for the phosphors to be placed for at least 0.5 hours in an environment where vapor is present.
  • the pressure is preferably at least 0.2 MPa, and even more preferably at least 0.3 MPa, and is generally 10 MPa or less, preferably 1 MPa or less, and more preferably 0.5 MPa or less.
  • the vapor is preferably saturated vapor (the vapor when a vapor phase and a liquid phase are present together in equilibrium under a given fixed pressure).
  • the phosphors should be placed in this environment for preferably at least 1 hour, and more preferably at least 1.5 hours, and for generally 12 hours or less, preferably 5 hours or less, and more preferably 3 hours or less.
  • the phosphors should be placed in a vessel made of alumina, porcelain or the like and placed in an autoclave. Steps such as acid washing, classification and surface treatment may be carried out beforehand on the phosphors, although desirable effects can be obtained even when the fired phosphors are used as is.
  • the surface of the phosphors may be subjected to surface treatment if necessary such as covering the surfaces with some foreign compound, in order to improve weatherability such as moisture resistance or to improve dispersibility in a resin in the phosphor-containing part of the light emitting device described later.
  • the surface treatment may be performed before or after a vapor heat treatment step. Unless the surface treatment prevents the presence of special adsorbed water obtained by the vapor heat treatment or has the effect of removing the adsorbed water, both of the treatments may be performed at the same time.
  • the emission spectrum was measured using a 150 W Xenon lamp as the excitation light source and using an MCPD 7000 (Otsuka Electronics Co., Ltd.) as the spectrometer.
  • An emission spectrum was obtained by measuring the emission intensity at each wavelength with the spectrometer over a wavelength range of from 380 nm to 800 nm using excitation light having a wavelength of 455 nm.
  • the color coordinates of x, y colorimetric system were calculated, as color coordinates x and y of the XYZ colorimetric system defined in JIS Z8701, by a method in accordance with JIS Z8724 from the data of the emission spectra in the wavelength region of from 480 nm to 780 nm obtained by the above-mentioned method.
  • Relative luminance is represented by a relative value when YAG (Product Number: P46-Y3) manufactured by Kasei Optonix Co., Ltd. is excited with light at the wavelength of 455 nm and when the value Y of the XYZ colorimetric system is set at 100.
  • the internal quantum efficiency was measured using a FP-6500 (JASCO Corporation).
  • the amount of sample used for measurement was 1 g, and measurement was carried out at an excitation wavelength of 455 nm. Emission was measured in the range of 480 to 780 nm.
  • the particle diameter was measured by the electrical sensing zone method using a Coulter Multisizer II (Beckman Coulter).
  • the aperture size used was 100 ⁇ m, and measurement was carried out after first ultrasonically dispersing the phosphors in water.
  • a BET specific surface area analyzer MS-9 (Yuasa Ionics KK) was used for measurement. About 1.3 g of phosphors was charged into a U-tube and degassed for 15 minutes at 150° C., following which nitrogen adsorption was effected and the specific surface area was computed from the quantity of adsorbed nitrogen using the principle of the BET 1-point method.
  • Analysis of the quantity of adsorbed water was carried out with a gas analyzer.
  • the quantity of emitted gas was analyzed by measurement with a gas analyzer for phosphor analysis (ANELVA) using an M-QA200TS (ANELVA) as the detector for mass spectroscopic analysis.
  • the gas having a molecular weight of 18 is regarded as water. 0.15 g of phosphors was used and measurement was carried out while the temperature was raised to 1000° C. at a rate of 33° C./min.
  • Infrared absorption spectroscopy was carried out with an AVATOR 360 (Nicolet), and spectral data acquisition and conversion using the Kubelka-Munk function were carried out with software (OMNIC E.S.P.) supplied with the spectrometer. Measurement was carried out under the following conditions: number of scans, 32; resolution, 4; and while passing a stream of nitrogen gas over the sample stage during measurement.
  • the weighed out raw materials were mixed together in a ball mill, then passed through a nylon mesh sieve, thereby preparing the raw materials.
  • the operations from weighing out to preparation were carried out within a glove box having a nitrogen atmosphere with an oxygen concentration of 1% or less, and ball milling was carried out in a double vessel set out in open air that consisted of a nitrogen-sealed plastic pot within a similarly nitrogen-sealed closed vessel.
  • Nylon-coated iron balls were used as the ball mill media (balls).
  • the prepared raw materials were charged into a Mo crucible and set within an electric furnace.
  • the internal temperature was raised to 1550° C. and held at 1550° C. for 8 hours, following which temperature ramp-down was begun, bringing firing treatment to completion and yielding phosphors.
  • the fired phosphors were passed through a nylon mesh sieve, ground in a ball mill and agitated for at least 1 hour in 1N hydrochloric acid, and subsequently rinsed with water.
  • the washed phosphors were then dewatered, dried in a hot-air dryer at 120° C., and recovered by being passed through a nylon mesh sieve.
  • the phosphors obtained in the above washing step were placed in a glass sample bottle, following which this sample bottle was set in an autoclave (Hiclave HG-50, Hirayama Manufacturing Corp.) and left to stand for 20 hours.
  • the environment within the autoclave was saturated steam, 135° C. and 0.33 MPa.
  • the above-mentioned pressure value is the pressure indicated on the autoclave (differential pressure with normal pressure) to which the normal pressure of 0.1 MPa has been added.
  • the phosphors were dried for 2 hours in a 140° C. hot-air dryer, giving the finished Phosphors 1.
  • the color coordinates, luminance and particle diameter of the resulting phosphors are shown in Table 1.
  • FIG. 1 shows the values obtained by converting the resulting infrared absorption spectrum to Kubelka-Munk function values.
  • Phosphors 2 were obtained in the same way as in Example 1. The color coordinates, luminance and particle diameter of the resulting phosphors are shown in Table 1.
  • FIG. 2 shows the values obtained by converting the resulting infrared absorption spectrum to Kubelka-Munk function values.
  • Phosphors 3 were obtained in the same way as in Example 1. The color coordinates, luminance and particle diameter of the resulting phosphors are shown in Table 1.
  • FIG. 3 shows the values obtained by converting the resulting infrared absorption spectrum to Kubelka-Munk function values.
  • Phosphors 4 were obtained in the same way as in Example 3.
  • the color coordinates, luminance and particle diameter of the resulting phosphors are shown in Table 1.
  • FIG. 4 shows the values obtained by converting the resulting infrared absorption spectrum to Kubelka-Munk function values.
  • Phosphors 5 were obtained in the same way as in Example 1.
  • the color coordinates, luminance and particle diameter of the resulting phosphors are shown in Table 1.
  • FIG. 5 shows the values obtained by converting the resulting infrared absorption spectrum to Kubelka-Munk function values.
  • the weighed out raw materials were mixed together using a mortar and pestle, then passed through a nylon mesh sieve, thereby preparing the raw material.
  • the operations from weighing out to preparation were carried out within a glove box having a nitrogen atmosphere with an oxygen concentration of 1% or less.
  • the prepared raw materials were charged into a Mo crucible and set within an electric furnace equipped with a tungsten heater.
  • the internal temperature was raised to 1300° C. and held for 4 hours, thereby carrying out initial firing.
  • the fired product obtained after initial firing was ground up using a mortar and pestle within the glovebox, then passed through a nylon mesh sieve.
  • the temperature within the furnace was then ramped up to 1525° C. and held at that temperature for 15 hours, following which temperature ramp-down was begun, bringing firing treatment to completion and yielding phosphors.
  • the fired phosphors were agitated for 3 hours in 1N hydrochloric acid and then rinsed with water. Next, the phosphors were dewatered, then dried in a hot-air dryer at 150° C. and recovered by being passed through a nylon mesh sieve.
  • the phosphors obtained in the above washing step were placed in a glass sample bottle, following which this sample bottle was set in an autoclave (Hiclave HG-50, Hirayama Manufacturing Corp.) and left to stand for 20 hours.
  • the environment within the autoclave was saturated steam, 135° C. and 0.33 MPa.
  • the above-mentioned pressure value is the pressure indicated on the autoclave (differential pressure with normal pressure) to which the normal pressure of 0.1 MPa has been added.
  • the phosphors after standing in the autoclave were dried 2 hours in a 140° C. hot-air dryer, giving the finished Phosphors 6.
  • the color coordinates, luminance and particle diameter of the resulting phosphors are shown in Table 1.
  • FIG. 6 shows the values obtained by converting the resulting infrared absorption spectrum to Kubelka-Munk function values.
  • FIGS. 1 to 5 show the infrared absorption spectra for Comparative Phosphors 1 to 5.
  • Example 1 0.425 0.555 137 30.6
  • Example 2 0.419 0.558 139 19.6
  • Example 3 0.419 0.559 139 20.3
  • Example 4 0.423 0.553 82 28.2
  • Example 5 0.408 0.563 118 6.7
  • Example 6 0.429 0.553 145 28.8 Comparative 0.424 0.555 125 29.7
  • Example 1 Comparative 0.420 0.557 125 19.1
  • Example 2 Comparative 0.420 0.558 127 19.8
  • Example 3 Comparative 0.424 0.552 75 27.7
  • Example 4 Comparative 0.409 0.561 108 6.8
  • Example 5 Comparative 0.427 0.554 136 28.8
  • Tables 2 and 3 show respectively (a) the values obtained by converting the absorption spectrum into Kubelka-Munk function values, and (b) the slopes between two adjoining measured values.
  • the value in the 3593 cm ⁇ 1 row has been calculated using the 3593 cm ⁇ 1 and 3595 cm ⁇ 1 values. This is thus the value of the slope between two points determined using the value of the neighboring point on the large value side.
  • the slope at 3608 cm ⁇ 1 is calculated using the 3610 cm ⁇ 1 value.
  • the average of the (b) values in Example 1 is ⁇ 5.000E ⁇ 02 (exponential notation using the symbol E). When this is divided by 1.508E+01, which is the maximum value in the range from 3250 cm ⁇ 1 to 3500 cm ⁇ 1 , the result is ⁇ 3.3E ⁇ 03.
  • the average of (b) is ⁇ 9.592E ⁇ 03; when this is divided by 1.151E+01, which is the maximum value in the range from 3250 cm ⁇ 1 to 3500 cm ⁇ 1 , the result is ⁇ 8.3E ⁇ 04.
  • Table 4 similarly gives the Kubelka-Munk function values for Example 2, their slopes and a maximum value.
  • Table 5 gives the values for Comparative Example 2
  • Table 6 gives the values for Example 3
  • Table 7 gives the values for Comparative Example 3
  • Table 8 gives the values for Example 4
  • Table 9 gives the values for Comparative Example 4
  • Table 10 gives the values for Example 5
  • Table 11 gives the values for Comparative Example 5
  • Table 12 gives the values for Example 6. The calculated results are shown in Table 13.
  • FIG. 7 is a graph in which (d) values at 3601 cm ⁇ 1 have been plotted, each (d) value being a numerical values obtained by, for the above (b) values, calculating the average of 5 measured values before and after a measurement wavelength (a total of 9 points) as a (c) value, and dividing the (c) value by the maximum value. It is apparent from the graph that there are clear differences between the values obtained for Phosphors 1 to 6 in the Examples of the invention and the values obtained for Comparative Phosphors 1 to 5. By calculating such parameters, it can easily be determined whether the phosphors obtained are phosphors according to the invention.
  • Table 14 shows, for the phosphors in Example 1 and Comparative Example 1, the specific surface areas as the values (a) determined by the above-described BET 1-point method, the values (b) calculated by the Coulter counter method using the above-described formula, and the ratios therebetween. It is apparent that, in the phosphors of the invention, the surface area determined by the BET method greatly decreases, as a result of which the value (a)/(b) becomes 20 or less.
  • the weighed out raw materials were mixed together in a mortar, then passed through a nylon mesh sieve, thereby preparing the raw material.
  • the operations from weighing out to preparation were carried out within a glove box having a nitrogen atmosphere with an oxygen concentration of 1% or less.
  • the prepared raw materials were charged into a Mo crucible and set within an electric furnace.
  • the internal temperature was raised to 1550° C. and held at 1550° C. for 8 hours, following which temperature ramp-down was begun, bring firing treatment to completion and yielding phosphors.
  • the fired phosphors were passed through a nylon mesh sieve, then agitated for at least 1 hour in 1N hydrochloric acid, and subsequently rinsed with water and dewatered.
  • the washed phosphors were then dried in a hot-air dryer at 120° C., and recovered by being passed through a nylon mesh sieve.
  • the phosphors obtained in the above washing step were placed in a glass sample bottle, following which this sample bottle was set in an autoclave (Hiclave HG-50, Hirayama Manufacturing Corp.) and left to stand for 20 hours.
  • the environment within the autoclave was saturated steam, 135° C. and 0.33 MPa.
  • the above-mentioned pressure value is the pressure indicated on the autoclave (differential pressure with normal pressure) to which the normal pressure of 0.1 MPa has been added.
  • the phosphors were dried for 2 hours in a 140° C. hot-air dryer, giving the finished phosphors.
  • the color coordinates and luminance of the resulting phosphors are shown in Table 16.
  • Example 7 Aside from not carrying out vapor heat treatment, the phosphors of Comparative Example 7 were produced in the same way as in Example 7. Also, aside from not carrying out vapor heat treatment, the phosphors of Comparative Example 8 were produced in the same way as in Example 8. The color coordinates and luminances of the resulting phosphors are shown in Table 16.
  • the weighed out raw materials were mixed together, then passed through a nylon mesh sieve, thereby preparing the raw material.
  • the operations from weighing out to preparation were carried out within a glove box having a nitrogen atmosphere with an oxygen concentration of 1% or less.
  • the prepared raw materials were charged into a Mo crucible and set within an electric furnace equipped with a tungsten heater.
  • the internal temperature was raised to 1550° C. and held at 1550° C. for 12 hours, following which temperature ramp-down was begun, bringing firing treatment to completion and yielding phosphors.
  • the fired phosphors were passed through a nylon mesh sieve, then agitated for at least 1 hour in 1N hydrochloric acid, and subsequently rinsed with water and dewatered.
  • the weighed out raw materials were mixed together, then passed through a nylon mesh sieve, thereby preparing the raw material.
  • the operations from weighing out to preparation were carried out within a glove box having a nitrogen atmosphere with an oxygen concentration of 1% or less.
  • the weighed out raw materials were mixed together, then passed through a nylon mesh sieve, thereby preparing the raw material.
  • the operations from weighing out to preparation were carried out within a glove box having a nitrogen atmosphere with an oxygen concentration of 1% or less.
  • the prepared raw materials were charged into a Mo crucible and set within an electric furnace equipped with a tungsten heater.
  • the interior of the furnace was evacuated, following which the internal temperature was raised to 300° C.
  • initial firing was carried out by raising the internal temperature to 1350° C. and holding that temperature for 4 hours.
  • the fired product after initial firing was ground using a mortar and pestle within a glovebox, then passed through a nylon mesh sieve.
  • the temperature within the furnace was then raised to 1525° C. and held at that temperature for 12 hours, following which temperature ramp-down was begun, bringing firing treatment to completion and yielding phosphors.
  • the weighed out raw materials were mixed together, then passed through a nylon mesh sieve, thereby preparing the raw material.
  • the operations from weighing out to preparation were carried out within a glove box having a nitrogen atmosphere with an oxygen concentration of 1% or less.
  • 5 wt % (based on the weight of the overall raw materials) of La 3 Si 6 N 11 :Ce phosphors was weighed out as a raw material.
  • the weighed out raw materials were mixed together, then passed through a nylon mesh sieve, thereby preparing the raw material.
  • the operations from weighing out to preparation were carried out within a glove box having a nitrogen atmosphere with an oxygen concentration of 1% or less.
  • Example 11 This was fired under the same firing conditions as in Example 11, and a washing step carried out under the same conditions as in Example 1.
  • the phosphors obtained in the above washing step were placed in a glass sample bottle, following which this sample bottle was set in high-temperature, high-humidity tester (PC-305S, Hirayama Manufacturing Corp.) and left to stand for 40 hours.
  • the environment within the autoclave was saturated steam, 158° C. and 0.49 MPa.
  • the above-mentioned pressure value is the pressure indicated on the autoclave (differential pressure with normal pressure) to which the normal pressure of 0.1 MPa has been added.
  • the phosphors were dried for 2 hours in a 140° C. hot-air dryer, giving the finished Phosphors 13.
  • the calculated values thus obtained are shown in FIG. 14 .
  • the white triangles in FIG. 14 represent the values of Comparative Examples in which vapor heat treatment was not carried out, and the black squares represent the values of Examples in which vapor heat treatment was carried out. It is apparent here that the Examples and the Comparative Examples can be clearly distinguished as specified in the first aspect of the invention.
  • the moisture desorbs at higher temperatures than normal, with at least 251 of the entire amount of adsorbed water desorbing at between 170° C. and 300° C.
  • the proportion of water that desorbs at between 170° C. and 300° C. is at most only 21% with, as shown in the respective figures, the proportion of water that desorbs at below 170° C. being highest.
  • the amount of water which desorbs at 170° C. or more and 300° C. or less is highest and accounts for at least 251 of the total.
  • This invention is able to provide phosphors having a high luminance and high efficiency. Particularly when used in white LEDs, these phosphors can be advantageously used for illumination and backlights in displays.

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JP2017036430A (ja) * 2015-08-07 2017-02-16 日亜化学工業株式会社 βサイアロン蛍光体の製造方法
US9920244B2 (en) 2013-02-07 2018-03-20 Mitsubishi Chemical Corporation Nitride phosphor and method for producing the same
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US9920244B2 (en) 2013-02-07 2018-03-20 Mitsubishi Chemical Corporation Nitride phosphor and method for producing the same
JP2017036430A (ja) * 2015-08-07 2017-02-16 日亜化学工業株式会社 βサイアロン蛍光体の製造方法
US11279875B2 (en) * 2017-07-19 2022-03-22 Mitsubishi Chemical Corporation Nitride phosphor and method for producing nitride phosphor

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EP2781577A4 (en) 2015-03-25
CN103946340A (zh) 2014-07-23

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